Self-draining heat exchanger

Abstract

A self-draining heat exchanger that is particularly adaptable in solar heat systems that drains automatically when the flow of liquid such as water is interrupted. The exchanger includes a plurality of tubes arranged for sequential flow of liquid therethrough with drainage valve means that are held closed by the inflowing liquid and that are opened by the weight of the liquid within the heat exchanger when this flow is interrupted to drain the liquid containing parts of the heat exchanger.

We claim: 
     
       1. A self-draining heat exchanger, comprising: liquid flow means including a plurality of tubes arranged for sequential flow of liquid through said tubes; a liquid inlet means into a first said tube in the series; an outlet liquid means communicating with a last said tube of said series; reverse flow means adjacent to said inlet means for flow of liquid from the heat exchanger into and back through said inlet means when liquid flow is interrupted; pressure operated valve means for closing said reverse flow means by pressure of liquid flowing through said tubes; means for interrupting closing pressure on said reverse flow valve means when liquid flow is interrupted, thereby permitting the pressure of liquid within said heat exchanger to open said valves for reverse flow of liquid from said heat exchanger back through said inlet means; said tubes being parallel with adjacent ends interconnected by two sets of flow chambers, a first set being adjacent to said inlet means and a second set being adjacent to said outlet means; and a flow manifold at at least said first set of flow chambers, liquid flow opening means between at least said first set of chambers and said manifold, said manifold connected to said liquid inlet, and said valve means positioned in the opening to control flow through the opening responsive to the liquid pressure in said manifold. 
     
     
       2. The heat exchanger of claim 1 wherein there is provided a said valve means between the manifold and the liquid inlet. 
     
     
       3. The heat exchanger of claim 2 wherein said valve means is positioned in an auxiliary chamber communicating with both the liquid inlet means and the manifold in which said valve means is located. 
     
     
       4. The heat exchanger of claim 1 wherein said heat exchanger tubes are essentially horizontal. 
     
     
       5. The heat exchanger of claim 1 wherein said heat exchanger tubes are essentially vertical. 
     
     
       6. The heat exchanger of claim 1 wherein said tubes are essentially parallel and closely adjacent, the adjacent tubes having interconnecting serpentine fins for heat transfer between external fluid and liquid flowing through said tubes.